It is known to provide ramp systems for vehicles such as buses in order to assist elderly and disabled passengers in entering and exiting such vehicles. In many cases, the ramp systems include a portion that can be extended out of the vehicle during boarding and deboarding, and then retracted into the vehicle so that the ramp does not interfere with the vehicle as it travels.
Numerous vehicle ramp systems are known in the art. One example of a vehicle ramp system is shown and described in U.S. Patent Application Publication No. 2008/0187425 in the name of Morris et al.
An important challenge in designing vehicle ramp systems is to accommodate a wide variety of circumstances, such as passengers in wheelchairs and scooters, passengers using walkers, and passengers having limited mobility but who can walk without assistive devices, any of whom may be boarding from curbed sidewalks of varying heights, and at various distances from the side of the vehicle, or boarding from the same road surface on which the vehicle rests. Such design challenges are compounded by the need to be able to retract the ramp system into a sufficiently compact space to meet the constraints of the vehicle to which the ramp system will be mounted, such as chassis space, floor space, and the like.